Shaft-to-hub coupling

ABSTRACT

A shaft is coupled to a hub by means of a resilient,helical, wire coil threadedly received in matching grooves formed externally on a cylindrical shaft section and internally within a cylindrical opening in the hub. The land sections between respective grooves in the shaft section and in the hub opening are of substantial extent and closely engage one another. A tight, torque-transmitting coupling is afforded, which coupling is capable of ready assembly and disassembly.

[ 1 SHAFT-TO-HUB COUPLING [75] Inventor: lrvin E. McWethy, Oxford, Ohio[73] Assignee: Phllco-Ford Corporation, Philadelphia, Pa.

[22] Filed: Dec. 30, 1971 [21] Appl. No.: 214,078

[52] U.S.Ci. .1 287/53 R, 92/255 [51] Int. Cl. ..F16d1/06 [58] Field ofSearch 287/53 R, 20 P; 85/46, 32 CS; 151/14 cs; 92/255 [56] ReferencesCited UNITED STATES PATENTS "782,349 2/1905 Marshall; ..ss/32cs2,361,244 10/1944 Smith ..2s7/2o1 1451 July 3,1973

2,512,316 6/1950 Eckener 85/46 X 3,177,782 4/1965 Sampson 287/125Primary Examiner-Andrew V. Kundrat Attorney Roben D. Sanborn [57]ABSTRACT A shaft is coupled to a hub by means of a resilient,helical,wire coil threadedly received in matching grooves formed externally on acylindrical shaft section and internally within a cylindrical opening inthe hub. The land sections between respective grooves in the shaftsection and in the hub opening are of substantial extent and closelyengage one another. A tight, torquetransmitting coupling is afforded,which coupling is capable of ready assembly and disassembly.

5 Claims, 6 Drawing; Figures SllllAFT-TO-HUIB COUPLING BACKGROUND OF THEINVENTION This invention relates to shaft couplings for hubs or thelike. The invention is particularly useful in the coupling of arotational shaft with the hub of a clutch plate.

In the field of automotive air conditioning, for example, refrigerantcompressors commonly are driven by the main engine through a belt andpulley arrangement. To modulate the refrigerating effect, one pulleydrives the compressor main shaft through a clutch that typicallyincludes a driven friction plate that is coupled to this shaft, and isboth engageable and disengageable by a driving plate, in response tooperation of a temperature sensing device. A drive arrangement of thistype characteristically is subject to both pulsating and impact loads,with resultant subjection of contacting clutch plate hub and shaftregions to slight relative motions that are conducive to frettingcorrosion, and possible resultant failure of the hub-to-shaft coupling.

It is a general objective of this invention to provide improvedshaft-to-hub coupling means that substantially eliminates frettingcorrosion, and facilitates both assembly and disassembly of the drivecoupling between a rotational shaft and the hub of a rotating member.

SUMMARY OF THE INVENTION In achievement of the foregoing as well asother objectives and advantages, the invention contemplates theprovision, in a shaft-to-hub coupling, of a shaft having a generallycylindrical section provided with a helical groove, and a hub having agenerally cylindrical opening receiving said shaft section and having ahelical groove matching the helical groove in said shaft section. Boththe grooved shaft section and the grooved hub opening include landsurface areas of substantial extent disposed in close fitting engagementwith one another, and a helical wire coil is threadedly received in saidmatching helical grooves to provide a selftightening, torquetransmissive threaded coupling between said shaft and said hub. I

The manner in which the foregoing as well as other objectives andadvantages of the invention may best be achieved will be more fullyunderstood from a consideration of the following description taken inlight of the accompanying drawing. I

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational showing of aportion of an automotive air conditioning apparatus embodying theinvention, some parts being shown diagrammatically and DESCRIPTION OFTHE PREFERRED EMBODIMENTS 18 supported in cantilever fashion on leafsprings 19 affixed to a flange 20 on stub shaft 16. The stub shaft 16for drive plate means 17 is rotatably supported in a bearing 24 providedin the clutch housing 25, and the compressor main shaft 22 is rotatablysupported in a suitable bearing 26 provided in an adjacent end wall 27of the compressor housing 31. A driven clutch plate 21 is attached, in anovel and improved manner to be described below, to compressor mainshaft 22. Clutch plate 21 is selectively engageable by friction ring 18of drive plate means 17, through selective energization andde-energization of a solenoid of conventional design and designatedgenerally by the numeral 23. It will be appreciated that springs 19provide both for torque transmission between flange 20 and ring 18, andfor axial movement of ring 18 in provision of its aforementionedselective engagement with clutch plate 21.

With reference also to FIGS. 2, 3 and 4, and in especial accordance withthe invention, driven clutch plate 21 includes a hub 32 provided with aninternal helical groove 33, and a corresponding portion of shaft 22includes an external helical groove 34 matching the internal groove 33.A helical spring 35 is threaded into the matching grooves 33, 34, and,preferably in cooperation with stop means such as a threaded thrust plug36, serves as the means by which plate 21 is fastened to shaft 22.

others broken away for convenience, and illustrating elements of aclutch plate and the mode of attachment of its hub to arefrigerantcompressor main shaft, in accordance with the invention;

FIG. 2 is a showing of a portion of the clutch plate as seen looking inthe direction of arrows 2-2 applied to FIG. 1;

FIG. 3 is an enlarged, fragmentary, sectional showing of the clutchplate hub and shaft coupling seen in FIGS. land 2; Y

FIG. 1 is an exploded view of the parts seen in FIG. 3; and

FIGS. 3 and 6 are, respectively, views similar to portions of FIG. 1 andFIG. 2, and illustrating a modification contemplated by the invention.

As is seen to advantage in FIGS. 3 and 4, a thrust plug 36 includesthreads 37 received within suitably matching threads 41 formed in theleft hand region of hub 32, as viewed in the drawing, and the end wallof plug 36 abuttingly engages the end of the shaft 22. As is best seenin FIG. 2, plug 36 is provided with a wrenchreceiving recess 42 by whichthe plug may be rotated for axial movements in the hub 32. Axialpositioning of plug 36 establishes and maintains the desired degree ofaxial extension of the threaded portion of shaft 22 into the threadedportion of the clutch plate hub. Considered another way, plug 36 servesas means disposed to react-between shaft 22 and hub 32 for establishingand maintaining predetermined axial positioning of the threaded hubsection on the threaded shaft section. In order to ensure against changeof the desired preset plug position, the thread angles of the plug 36and the helical spring 35 are the reverse of one another. Rotation ofclutch plate 21 is in a direction tending to cause it to thread itselfonto shaft 223, but further relative threading motion is prevented byabutting engagement of the end of shaft 22 with the flat end face ofplug 36; the same rotation tends to cause plug 36 to thread itself intothe hub 32. It will therefore be appreciated that clutch plate 17 is, ineffect, locked onto shaft 22 as a result of the coaction of the abovedescribed threads. The clutch plate 21 may be readily removed from theshaft, such as may be desired when servicing, merely by rotating theplate relative to shaft 22 in a direction opposite to its normaldirection of rotation.

As seen to further advantage in FIG. 3, helical grooves 33 and 34preferably are of standard 60 thread form, and have a pitch of fivegrooves per inch. The grooves 34 in shaft 22 have a pitch diameter ofabout 0.450 inch, the diameter of the shaft in this region being about0.500 inch. The grooves 33 in the 0.500 inch diameter opening in hub 32have a pitch diameter of about 0.560 inch. The pitch angle is relativelylow, being about 8 to 12. Insert 35 is a helical spring, of generallydiamond-shaped cross-section, and when in place affords a standardthread size of about 0.500 inch five threads per inch, right-handed. Inaddition to threaded connection between the hub and shaft, it will beappreciated that the generally cylindrical, extended land areas betweenthe grooves afford a precision fit that minimizes relative movements ofa vibrational nature between the hub and the shaft. From theillustration in in FIG. 4, it will be appreciated that, for the sake ofconvenience of assembly, helical spring 35 can be wound either over orunder size relative to the diameters of the connecting portion of shaft22 and hub 32, so that the spring may be preassembled either to the hubor to the shaft.

Still with reference to FIGS. 3 and 4, the threads 37 of thrust plug 36,and the mating threads 41 of hub 32, are of standard 60 thread form,having a pitch diameter of about 11 16th inch, and comprise twelvelefthanded threads per inch.

In the embodiment of the invention shown in FIGS. and 6, axial movementof a clutch plate 121 along shaft 122, to which it is threadedly keyed,is prevented by a thrust plate 43, instead of a threaded plug, affixedto the clutch plate by screws S and positioned to extend over thethreaded opening in the plate hub for abutting engagement with the endof shaft 122. An arrangement such as this 'may be desirable in aninstance where axial adjustment of clutch plate 121 on shaft 122 neednot be provided.

While in the illustrated embodiments of the invention the threaded shaftand hub sections are of generally cylindrical shape, it will beunderstood that these same sections may be slightly tapered while stillaffording threaded connection between the hub and shaft. Thus, the termgenerally cylindrical contemplates either form. These as well as othermodifications are contemplated by the scope of the appended claims.

From the foregoing, it will be appreciated that the invention affords animproved shaftto-hub coupling that substantially eliminates frettingcorrosion, and facilitates both assembly and disassembly of the drivecoupling between a rotational shaft and the hub of a rotatable member.

I claim:

1. In a shaft to hub coupling: a shaft having a generally cylindricalsection provided with a helical groove and an end; means defining a hubhaving a generally cylindrical opening receiving said shaft section andhaving a helical groove matching the helical groove in said shaftsection; each said shaft section and said hub opening including landareas of substantial extent between their respective-grooves anddisposed in close fitting engagement with one another; a helical wirecoil threadedly received in said matching helical groove in provision ofa threaded coupling between said shaft and said hub; and stop meanscomprising a member releasably affixed to said hub, extending over saidhub opening, and disposed in abutting engagement with the end of saidgenerally cylindrical shaft section, said stop means being effective toestablish and maintain predetermined axial positioning of the threadedhub on the threaded shaft section.

2. A coupling according to claim 1, and characterized further in thatsaid stop means disposed in abutting engagement with said shaft sectioncomprises a plate releasably affixed to said hub.

3. A coupling according to claim 1, and characterized further in thatsaid stop means disposed in abutting engagement with said shaft sectioncomprises plug means threadedly retained in a second set of threadsprovided in the hub opening.

4. A coupling according to claim 3, and characterized in that each saidhelical coil and its matching grooves are of helical extent to theopposite hand as respects the helical extent of the helical threads onsaid plug means and its matching threads in said hub opening.

5. A torque transmissive shaft and hub assembly comprising: a shafthaving an end and a generally cylindrical portion provided with ahelical groove; means defining a hub having a generally cylindricalopening receiving said shaft cylindrical portion and having a helicalgroove matching the helical groove in said shaft cylindrical portion;each said shaft cylindrical portion and said hub opening including landareas of substantial extent between their respective grooves anddisposed in close fitting engagement with one another; a helical wirecoil threadedly received in said matching helical grooves in provisionof a threaded coupling between said shaft and said hub; and stop meansincluding a member releasably affixed to said hub, extending over saidhub opening, and disposed in abutting engagement with said shaft end,said stop means being effective to react between said shaft end and saidhub to establish and maintain predetermined axial positioning of thethreaded hub section on the threaded shaft portion upon application oftorque to said assembly in a direction tending to thread said hub ontosaid shaft.

1. In a shaft to hub coupling: a shaft having a generally cylindricalsection provided with a helical groove and an end; means defining a hubhaving a generally cylindrical opening receiving said shaft section andhaving a helical groove matching the helical groove in said shaftsection; each said shaft section and said hub opening including landareas of substantial extent between their respective grooves anddisposed in close fitting engagement with one another; a helical wirecoil threadedly received in said matching helical groove in provision ofa threaded coupling between said shaft and said hub; and stop meanscomprising a member releasably affixed to said hub, extending over saidhub opening, and disposed in abutting engagement with the end of saidgenerally cylindrical shaft section, said stop means being effective toestablish and maintain predetermined axial positioning of the threadedhub on the threaded shaft section.
 2. A coupling according to claim 1,and characterized further in that said stop means disposed in abuttingengagement with said shaft section comprises a plate releasably affixedto said hub.
 3. A coupling according to claim 1, and characterizedfurther in that said stop means disposed in abutting engagement withsaid shaft section comprises plug means threadedly retained in a secondset of threads provided in the hub opening.
 4. A coupling according toclaim 3, and characterized in that each said helical coil and itsmatching grooves are of helical extent to the opposite hand as respectsthe helical extent of the helical threads on said plug means and itsmatching threads in said hub opening.
 5. A torque transmissive shaft andhub assembly comprising: a shaft having an end and a generallycylindrical portion provided with a helical groove; means defining a hubhaving a generally cylindrical opening receiving said shaft cylindricalportion and having a helical groove matching the helical groove in saidshaft cylindrical portion; each said shaft cylindrical portion and saidhub opening including land areas of substantial extent between theirrespective grooves and disposed in close fitting engagement with oneanother; a helical wire coil threadedly received in said matchinghelical grooves in provision of a threaded coupling between said shaftand said hub; and stop means including a member releasably affixed tosaid hub, extending over said hub opening, and disposed in abuttingengagement with said shaft end, said stop means being effective to reactbetween said shaft end and said hub to establish and maintainpredetermined axial positioning of the threaded hub section on thethreaded shaft portion upon application of torque to said assembly in adirection tending to thread said hub onto said shaft.